Relay control system



P 1952 H. c. LAWRENCE ETAL 2,611,808

RELAY CONTROL SYSTEM Filed Jan. 7, 1948 0, MW 2 w M W W m M J m 7: mm sapmrr/ WZAFEM F 95 F Patented Sept. 23, 1952 UNI TED S S T GTF F 1 (1E.2511308 I RELAY CONTROL SYSTEM ;HowardLawre'nce, Delaware Township,Camden County, and George Yewdall, Palmyra, N. J.,-as signor s'to=-Radio 'corp oration of Amer- I ica, acorporationof Delaware-Application .lanuary 7, 1948,Serial No. 1",032

This invention irelates to improvements. in re lay control devices andmore particularly to :re- .laytcontrol circuits in which the openingor-closing point 'of the relay israpproached slowly.

The problem of :relay contact chattering is a thermostatic control or insystems wherein "the :control is :governed by a motor. "It has beennecessary in the :past, in order to assure smooth operation and toprevent chattering "of the relay ac'ontacts, 'to 'use involved*circ'uits which :in

many-instancesrequire sseveralvacuum tubes. V

in systems "wherein the desired openin closing-point is approachedrapidly it is possible to incorporate either electrical .or :mec'hanicalinertia into: the system .so that the :relay "coasts =past :th'ecritical'apolnt' atiwhich lit .would totherwise chatter.Such-fa:systempnoweverpisnot possible when there :ar'e' times when theiopeningaor closing of the relay is approaohedcslowly.

It is a'n'object of 'this invention to eliminate the chattering of relaycontrol circuit in-which the opening or closing point is approached-slow1y.- a I It is another object of this invention toFprovide a methodof- :opemtingmemw in which an :auxiliary'operating voltage is utilizedtoprevent chatterin'gof the i lay contact's. I lt is stilllanother objectof this invention to provide a' relay having "an -auxilia'ry coil whichis energizedfand de-energizedsokas'to insuresmooth operation- 0f itherelay. r

Yet another object or this invention is to provide .-''a combination ofr-e'lays which. will .1 operate a control system :in @such :Iashi'onthat there will b'e no chattering of the relaiy contacts These objectsare =achieved:ihaccordance with the invention iby providing -;a primaryrelaywith ah aux-iliary aidin'gelectromotivelorce. 1'I-he1aidmg forc'eis sw it'ched into operation in =9, isense such that it will-aid in theopening or closing, whichever :m'ay be taking 'place an'd isdisconnect'ed as soon as the operation is completed.

The above-and other objects and advantag'esof our invention "will becomeapparent upo'naconsiderationof the following detailed description takenin conjunction with {the accompanying drawinesinwh iehz r 7 4 -Figur'e1- represents sc' 'enfaticaiiy an embodiment' 'of the invention asapplied t'othe control eta-transmitter; g

"Figure 2 1's a'schematic diagram representin a modified form of*thei'riVhtioh;

4"'Claims. (Cl. 175-320) 2 "-Figure 3 is a schematic representationofone means of accomplishing the resultsof the'inventiojn utilizinga .pluralityofrelays;

Figure 4 I represents schematically a modification of the invention foruse incircuits where only on'and off operations are to becontrolled; nFigure 5 representsschematically a'controlsys tem-adapted .for use withany ofgthe arrangements shown inFigures 1, 2 and 3.

-' Referring to Figure 1, it will be seen that there has been provided avacuum tube V1 having in its cathode circuit one coil L1 ofa relayKi Therelay K1 is also provided with an operating coil L2, electromagneticallyopposed to L1, and an auxiliary coilLa. The armature-of the relay is ofthe balancedgtypeand comprises in efiect a double-pole double-throw-switch having .a neutral position. Such relays -wi th the exception ofthe EauaiIiary coil arefwell known in the art and anysuitable -type maybe'used; A suitable sourceof direct-current potential (not shown) isconnected :to operate oneficoiloLzt of" the relay through: a resistornetwork consisting of. center tapped resistor *R1 "and; :adjustableresistor R3. :Thissourceaof-ipotential is :aiso'connected directily to;;one contact 'C.0I1 "the armature "of the relay.- The center tap of. theresistor'Ri is con.- nected through the auxiliary coil'Lslandtheresistor Ra -t0 the contact'armfBrof thearmature of T the relay. Theother JOGIIEQCtHp'OinPA associated withthecont'act J'arm B isgrounded... The second' contaotfarm of the armature is "arrangedtonompl'e'te a circuit through'one ofits contacts Diatfsuch time as thecontact Ais' clos'ed and -t,o:'complet'e' a circuit toithe contaetatsuoh time as oontactiC'is'closed. i

h-For purposesof-illustratirig t" semen of assumed that the tube V1 -'isthejpow'er'am pli fier of a radio "frequency"transmitter and that itis'iies'iredto a'djust automatically the loadin'g circults ofthispo'we'r amplifier so thatfthe time will draw a "fixed predeterminedcathode current; The cathode current is, by means of the block i-ng:"c'ondenser K caused-to flow through the-operatiiig coil 111 of therelay. A 'similarfcurrent in duced by the source of control potent'iali's caused to flow through the other"operating coilEz offthe relay.Whenthe n1'agn tic rorce causes b y o'pra'ting coil lii equalsthattause'cl by ep y coil ;Lz the ai'mature assumesa nausea pos tion inwhichiall contacts'areopen. variable resistor R3 the baianc set for anydesired loading or the have amen:

; it will he fier. When the current through the coil L1 causes amagnetic force greater than that of the coil L2 contacts C and F will beclosed. Similarly, when the coil L2 exerts the greater magnetic forcecontacts A and D will be closed. The contact D and F together with thecontact bar E may be used to control any suitable apparatus which willrestablish the desired point of operation.

Again, for the purposes of illustration, it will be assumed that thecontacts D and F and the contact bar E are connected to a control systemsuch as illustrated in Figure with the connections being made to thecorresponding letters as shown in this figure. Referring to that system,it will be seen that there ha been provided a motor having forward andreverse windings. The motor is used to control the loading of an antennafrom a transmitter and thus the amount of current drawn by thetransmitter. As the loading motor causes the load adjustment to approachthe desired current the relay K1 of Figure 1, will tend to chattertowards its neutral position. This chattering results in noise in theassociated equipment and will cause the contacts of the relay to areand, therefore, burn out prematurely and in general result inunsatisfactory operation of the loading circuits.

This unsatisfactory operation of the loading circuits is overcome by theaddition of the coil L3 and the relay contacts A and C. It will be seenthat the coil L3 is connected to a source of voltage provided by thecenter tapped resistor R1; This coil is connected to contacts A and C insuch a way that when the operating coil Ll'iS exerting the largestforce, causing contactsFand C to be closed, the current in the-auxiliarycoil L3 acts inthe same direction as the current in the operating coilL1: That is to say, the field of the auxiliary coil aids that of theoperating C OiLLL This will cause the automatic loading motor to adjustthe loading closer to the exact desired loading position beforechattering occurs. The first time the relay opens as it startsto chatterthe current through the auxiliary :c'oil will be cut off by contact 0.There. is then 'no longer the field from theauxiliary coil aiding thatof the operating coil L1 and the relay thus cannot continue to chatter.I a l The current in the auxiliary coil must-be set low enough that italone will not cause the relay to stay closed. A typical value ofcurrent inthe auxiliary coil is such that if the control coils alone arecapable of adjusting theloading of the transmitter to within plus orminus! 5 milliamperes the auxiliary coil would have..a:.current equal to2 milliamperes. This would mean that the automatic loading motor wouldcausethe loading adjustment to come within 5 minus .2, or 3 milliamperespf the desired value. Thus, with the addition of the auxiliarycoil,'although the relay would tend to start chattering at plus orminus3 milliamperes from the desired value,- the first cycle of chatteringremoves the effect of the auxiliary coil, reestablishing the chatteringpoint to plus or minus 5 milliamperes. Since the adjustment is alreadywithin at least 3 milliamperes-of its normal value the relay, therefore,cannot continue to chatter. U i

The operation of thesystem when thexcurrent in theoperating coil L2 islargerthan that in the operating coil L will cause themotorto rotate ina direction opposite from thatvdescribed above and is similar exceptthat the current in the auxiliary coil is, reversed so that itwill.v aidthe control coil L2 rather than the control coil L1.

Results similar to the above may be obtained Without the use of anauxiliary coil by suitably switching shunting resistors across theoperating coils. A preferred embodiment of such an arrangement isillustrated in Figure 2.

Referring to that figure, it will be seen that it i quite similar to thearrangement shown in Fig. 1 with the exception that the source ofcontrol potential is added to one or the other of the operating coilsthrough the appropriate one of a pair of resistors R4, R5.

The operation of such a system is efiectively the same as that shown inFigure 1. The resistors R4, R5 are connected through the contacts A andB of the contact bar B of the armature of the relay so that when thecurrent in one of the operating coils Li, L; is greater than in theother, causing the corrective apparatus to operate to reduce thiscurrent to the desired value, the coil having the lesser current isshunted by one of the resistors.- Thus, the currentin the latter coil isreduced'by a small amount; for example, under conditions similar tothose assumed above, 2 milliamperes. It will be'clear that thisreduction in current produces the same results as were provided by theaddition of the auxiliary coil as shown in Fig. 1 and chattering isprevented.

It often occurs that thereis available for a particular operation, adifferential relay having only single-pole double-throw contacts ratherthan the double-pole double-throw contacts required by the embodimentsshown in Figures 1 and 2. In such case the advantages of the inventionmay be obtained byv the arrangement shown in Figure 3.

In order to simplify the understanding of this modification, thecircuits to becontrolled and themeans-by which the desired restorationis achieved, have not been included. It .will be understood that theymay be the same as described in-connection' with either Figure l orFigure 2., Furthermore, for purposes of illustration, the use of a pairof resistors rather than the auxiliary coil has been shown, although itwill'be obvious that either arrangement is-equally adapted to obtain thedesired'results. i

In: this, embodiment there has been provided a relay K2 similar in allrespects to the relay K1 of Figure ,1, with the exception that itsarmature. consists of a single contact bar ET arranged to complete acircuit to either of two contacts D. or F.

source of control potential .(not: shown) while the other contact I"*isficonnected-through the operating coil of arelay; K4. to, the samesource of control potential. The completion of these circuits is madethroughthe contact arm E pt the primary. relay K2. Each of theauxilialjrelays K: andKr-is provided with double-pole single-throw armatures.These, latter armatures .are, con nected to. the primary relay and theadjusting means in the same fashion as the contacts of the double-poledouble-throw armatures, described above were connected through resistorsB and The; operation of this systexnwill be -clear when it is noted thatan unbalance in the-pg arr re a za iu tes a mature n a in tion towardsthe operating coil .having the stronger field and, hence, that oneoj,the auxil iary relays K3 orK4 controlled by suchection. The actuation ofthe proper relay completeslcir:

One of these contacts'Df is connected through .theoperating coilof a,relay-Ka to a -cuits similar to-those a'lread-y describedzzand thedesired anti-chattering effect obtained.

The benefits of-the invention-mayz'also be obtained in relay controlsystems requiring an open- -ing and closingtype of'controlratherlthanlthe openforward-reverse control systems "disclosed above.Thermostatic controls :on 'iboilers rand chemical processesrequiring-close adjustmentzare an example of such applications.

An arrangement :applicable to SUCh'LSYStEIIIS'IlS shown in Figure 4.Again, in:order -to.;:a void undue complicationof the drawing,onlysoimuch of the apparatus as is necessary for ;a clearfunderstandingof the mode of operation has been shown. The adaptation "of thearrangement.

(not shown) is also connected to theoperating coil of theorelaythrough'aseries circuitxjconsisting of .an adjustable resistance R3 and.the :con-

tacts Iand J of one pole ofthe relay.- flhel'con- .tacts G and H of theother pole of therelay;-,are

connected, as will be understood,.'to the {corre 'ing circuit (notshown).

The'resistor is adjusted so that aislight increasein current flowsthrough the operatingcoil of the relay when the operating voltage issuch that the contacts are caused'to close. This additional current isremovedwhen the currenttinithe operating coil drops to such an extentthat the relay will begin to chatter towards the open position. Sincethe current will, by then, be adjusted to a point well within thechattering range, chattering will be impossible. Although aresistor hasbeen illustrated in connection with Figure 4, it will be obvious thatthe same effect may be accomplished by providing an auxiliary coil suchas shown in Figure 1 to produce the differential efiect.

It is to be noted that a further effect of any of the above describedembodiments is that they decrease the tolerance to which the relay willinitially adjust the controlled circuit. It was seen, in connection withFigure 1, that a relay capable of adjusting the controlled current towithin plus or minus 5 milliampe-res of the desired value could be madeto be within plus or minus 3 milliamperes by the aid of an auxiliarycoil of Figure l or the equivalent means shown in Figures 2 or 3. It canreadily be seen that by suitable adjustment the same relay could be usedto adjust the currents to within less than 1 milliampere of the desiredvalue. However, in such case, the relay will not again operate until thecurrent has changed :by a value equal to the differential current.

This invention, therefore, provides a relay control system in which useis made of an auxiliary force which causes original adjustment of thesystem to a point well within the normal chattering point and, at theinstant when chattering would otherwise start at the new tolerancepoint,

removes the auxiliary force whereby chattering is made impossible.

We claim:

1'. A relay system comprising, in combination, an armature havingalternative contacting positions and a neutral position, a pair ofoperating coils, one offsaid coils being adapted to be energized by acurrent to be controlled and being so "poledrthat:currenttherethroughstands:to cause movement of saidarmatureiin.cneldirectiongthe other df said coils ?being adapted to be energizediby 'a contrcl voltage and being 'so poled that cur- '=rent=therethroug*h tends :to cause movement of said armature in the oppositedirectiomifirs't and second current reducing devices, first and secondpairs of cooperating contacts on said armature,

" means ncluding said"-first-lpair of 1 contacts and saidt'currentreduci-ng device whereby actuation-of said armature from itsneutral position insaidone" direction closes said first -pairofconztacts and "connects said first current reducing -dei'rice intocircuitry withsaidother coil toreduce {the currentiflowing-therein,means includingsaid -second"pair* of contacts and said *second current"reducing device whereby-'actuation-df saidarrrra- "ture rorn itsmeutralposition in said otherdirection ,0 osesisaidjsecond-pair'of "contactsanaconnec'ts" said second currentreducing devices :into

1current-iipwingtherein.

,2 Agrel ay system comprising, in combination rmya-turah'aving'firstandsecond contact-closin positions andanintermediate neutral positioniatwvhich said contactsare open, said arma- "turegbeing "connected'ito'apoint "of "fixed reference "potential, first "and "secondelectromagnetically opposed operating :coilsysaid'first coil beingradaptedfto 3 16 fen'ergized"by asource of 'con'trol current,'sai'dsecond coil being 'adapted todbe "that whenthefield of saidfirstoperating coilis the strongest said armature moves to said firstcontact closing position and when the, field of said second operatingcoil is the strongest said armature moves to said second contact closingposition, means for connecting said source of control current inparallel with said first coil, means for connecting said current to becontrolled in parallel with said second coil, connections between oneend of each of said coils and a point of fixed reference potential,first and second current reducing devices, and means including saidcontacts, said coils and said current reducing devices whereby when saidarmature is moved to one of said contact closing positions the currentin the operating coil not causing such movement is reduced.

3. A relay system comprising, in combination, an armature having firstand second contact closing positions and an intermediate neutralposition at which said contacts are open, said armature being connectedto a point of fixed reference potential, first and secondelectromagnetically opposed operating coils, said first coil beinadapted to be energized by a source of control current, said second coilbeing adapted to be energized by a source of current to be controlled.said armature being actuated by the resultant field of said operatingcoils in a manner such that when the field of said first operating coilis the strongest said armature moves to said first contact closingposition and when the field of said second operating coil is thestrongest said armature moves to said second contact closing position,means for connecting said source of control current in parallel withsaid first coil, means for connecting said current to be controlled inparallel with said second coil, connections between one end of each ofsaid coils and a point of fixed reference potential, first and secondcurrent redevice to said first contacts.

. ture being connectedto a point of fixed reference potential, first andsecond electromagnetically opposed operating coils, said first coilbeing adapted to be energized by a source of control current, saidsecond coil being adapted to be energized by a source of current to becontrolled, said armature'being actuated by the resultant fieldof saidoperating coils in. a manner such that when the field of said firstoperating coil, is the strongest said armature moves to'said-fi'rst'contact closing position and when the field ofsaid second operatingcoil is the strongest said armature moves to said second contact closingposition, means for connecting said source of control current inparallel with said first coil,fmeans for connecting said current to becontrolled in parallel with said second coil, connections between 1 oneend of each of said coils and'a point, of fixed reference potential,first and second current reducing devices, third and fourth operatingcoils, one end of each of said third and fourth coils being adapted tobe connected to a source of current, the other ends of said third andfourth coils being connected respectively to said first and secondcontacts, third and fourth contact 0105- ing' armaturesoperativelyassociated with said third and'fourth coils respectively,said armatures being normally, openjand being moved to said contactclosingpositions; upon actuation of the .coil: associated therewith,said associated armatures being connected in series, the center junctionof said ,armatures. being connected to saidpoint of fixed-referencepotential, the other end of said first operating coil being-connectedthrough said first currentreducing device to said fourth contacts andthe other end of said second coilzbeing' connected through said secondcurrent reducing device to said third contacts.

HOWARD C. LAWRENCE. .GEORGE E. YEWDALL.

REFERENCES CITED The'following references are of record in the NumberNumber fileof'this patent:, I .V

rTEn'sTATEsPATENTs Name Date Delaney-L Dec. 5, 1893 1 Thomson; May 12,1903 -Mershon 'Mar. 27, 1906 'Hou'gh Nov. 4, 1930 Champlin Nov. 26, 1935Lamb May'26, 1936 West May 7, 1940 Kovalsky Aug. 26, 1941 Harris Oct.14, 1941 FOREIGN PATENTS Country Date Great'Britain Oct. 23, 1934

